wind energy proceedings of the euromech colloquium

Wind Energy
Proceedings of the Euromech Colloquium
123
Joachim Peinke, Peter Schaumann
Wind Energy
Colloquium
Proceedings of the Euromech
and Stephan Barth (Eds.)
With 199 Figures and 14 Tables
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ISBN-13 978-3-540-33865-9 S pringer Berlin Heidelberg New York
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Institute of Physics

26111 Oldenburg


University of Hannover
Institute for Steel Construction

Appelstrasse 9a
30167 Hannover
Dr. Stephan Barth
ForWind - Center for Wind Energy Research
Germany
Institute of Physics

26111 Oldenburg
Germany

Prof. Dr Ing. Peter Schaumann
Germany
Typesetting by the editors and SPi using Springer
ForWind - Center for Wind Energy Research
Carl-von-O ssietzky University O ldenburg Carl-von-O ssietzky University O ldenburg
Cover design: Eric h Kirchner, Heidelberg
schaumann@ stahl.uni-hannover.de
Prof. Dr. Joachim Peinke
ForWind - Center for Wind Energy Research

Preface
Wind energy is one of the prominent renewable energy sources on earth.
During the last decade there has been a tremendous growth, both in size
and power of wind energy converters (WECs). The global installed power has
increased from 7.5 GW in 1997 to more than 50 GW in 2005 (WWEA – March
2005). At the same time, turbines have grown from kW machines to 5 MW
turbines with rotor diameters of more than 100 m. This enormous develop-
ment and the more recent use in offshore application made high demands on
design, construction and operation of WECs. Thus not only a new major in-
dustry has been established but also a new interdisciplinary field of research
affecting scientists from engineering, physics and meteorology.
In order to tackle the problems and reservations in this interdiscipli-
nary community of wind energy scientists, ForWind, the Center for Wind
Energy Research of the Universities of Oldenburg and Hanover, arranged the
EUROMECH Colloquium 464b – Wind Energy, which was held from October
4, 7, 2005, at the Carl von Ossietzky University of Oldenburg, Germany. The
central aim of this colloquium was to bring together the up to then separate
communities of wind energy scientists and those who do fundamental research
in mechanics. Wind energy is a challenging task in mechanics and many of
future progress will find relevant applications in wind energy conversion.
More than 100 experts coming from 16 countries from all over the world
attended the meeting, confirming the need and the concept of this colloquium.
The 46 oral and 28 poster presentations were grouped in the following topics:
– Wind climate and wind field
– Gusts, extreme events and turbulence
– Power production and fluctuations
– Rotor aerodynamics
– Wake effects
– Materials, fatigue and structural health monitoring
Phenomenological approaches mainly based on experimental and empirical

data as well as advanced fundamental mathematical scientific approaches have
VI Preface
been presented, spanning the range from reliability investigations to new CFD
codes for turbulence models or Levy statistics of wind fluctuations.
During this meeting it became clear, which fundamental scientific tasks
will have essential importance for future developments in wind energy:
– A better understanding of the marine atmospheric boundary layer, ranging
from mean wind profiles to high resolved influences of turbulence. These
questions need further measurements as well as genuine simulations and
models. A proper and detailed wind field description is indispensable for
correct power and load modeling.
– CFD simulations for wind profiles and rotor aerodynamics with advanced
methods (aeroelastic codes) that include experimental details on the
dynamic stall phenomenon as well as near and far field rotor wakes.
– A site independent description of wind power production taking into
account turbulence induced fluctuations.
– Material loads of different components of a WEC and the fatigue recog-
nition of which due to the high number of lifecycles of such complex
machines.
– To establish an advanced numerical hybrid model for a 3D simulation of
a WEC, taking into account wind and wave loads as well as all effects of
operation in a so-called ‘integrated’ model.
Many intensive discussions on these and other topics took place between
participants from different disciplines during coffee and lunch breaks and
also during the social evening events reception of the city at the “ehema-
lige Exerzierhalle” and the conference dinner on the nightly lake of Bad
Zwischenahn.
The positive feedback for the meeting’s scientific and social aspects encour-
aged the scientific committee to decide to have follow-up meetings alternately
organized by Duwind, Risø and ForWind. All participants shared the opinion

that the scientific interdisciplinary cooperation and international collabora-
tion shall be intensified.
The organizers want to thank the scientific committee members Martin
K¨uhn, Gijs van Kuik, Soeren E. Larsen, Ramgopal Puthli and Daniel Schertzer
for helping to organize this conference and establishing this book. Further-
more, we are grateful for the financial support of the Federal Ministry of Edu-
cation and Research, the City of Oldenburg and the EWE company. Special
thanks go to Margret Warns, Elke Seidel, Moses K¨arn, Martin Grosser, Frank
B¨ottcher for organizing all technical and administrative concerns.
Contents
List of Contributors XXI
1 Offshore Wind Power Meteorology
Bernhard Lange 1
1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Offshore WindMeasurements 2
1.3 Offshore Meteorology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.4 Application to Wind Power Utilization . . . . . . . . . . . . . . . . . . . . . . . 4
1.5 Conclusion 5
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2 Wave Loads on Wind-Power Plants in Deep
and Shallow Water
Lars Bergdahl, Jenny Trumars and Claes Eskilsson 7
2.1 A Concept of Wave Design in Shallow Areas . . . . . . . . . . . . . . . . . . 7
2.2 Deep-Water Wave Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.3 Wave Transmission into a Shallow Area
Using a Phase-Averaging Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.4 Wave Kinematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.5 Example ofWaveLoads 10
2.6 Wave Transmission into a Shallow Area
UsingBoussinesq Models 12

2.7 Conclusions 12
2.8 Acknowledgements 12
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3 Time Domain Comparison of Simulated and Measured
Wind Turbine Loads Using Constrained Wind Fields
Wim Bierbooms and Dick Veldkamp 15
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.2 Constrained Stochastic Simulation of Wind Fields . . . . . . . . . . . . . 15
VIII Contents
3.3 Stochastic Wind Fields which Encompass Measured
WindSpeedSeries 16
3.4 Load Calculations Based on Normal and Constrained Wind
Field Simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.5 Comparison between Measured Loads and Calculated Ones
BasedonConstrainedWindFields 19
3.6 Conclusion 20
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4 Mean Wind and Turbulence in the Atmospheric Boundary
Layer Above the Surface Layer
S.E. Larsen, S.E. Gryning, N.O. Jensen, H.E. Jørgensen and J. Mann 21
4.1 Atmospheric Boundary Layers at Larger Heights . . . . . . . . . . . . . . 21
4.2 DatafromHøvsøre Test Site 22
4.3 Discussion 24
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
5 Wind Speed Profiles above the North Sea
J. Tambke, J.A.T. Bye, B. Lange and J O. Wolff 27
5.1 Theory of Inertially Coupled Wind Profiles (ICWP) . . . . . . . . . . . 27
5.2 Comparison to Observations at Horns Rev and FINO1 . . . . . . . . . 29
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
6 Fundamental Aspects of Fluid Flow over Complex Terrain

for Wind Energy Applications
Jos´eFern´andez Puga, Manfred Fallen and Fritz Ebert 33
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
6.2 ExperimentalSetup 34
6.3 Results 35
6.4 Conclusions 38
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
7 Models for Computer Simulation of Wind Flow
over Sparsely Forested Regions
J.C. Lopes da Costa, F.A. Castro and J.M. L.M. Palma 39
7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
7.2 Mathematical Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
7.3 Results 40
7.4 Conclusions 42
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
8 Power Performance via Nacelle Anemometry on Complex
Terrain
Etienne Bibor and Christian Masson 43
8.1 Introduction and Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
8.2 Experimental Installations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
8.3 ExperimentalAnalysis 43
Contents IX
8.4 Numerical Analysis 44
8.5 Results andAnalysis 44
8.5.1 Comparaison with the Manufacturer . . . . . . . . . . . . . . . . . . 44
8.5.2 Influence on the Wind Turbine Control . . . . . . . . . . . . . . . 44
8.5.3 Influence of the Terrain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
8.5.4 Numerical Validation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
8.6 Conclusion 46
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

9 Pollutant Dispersion in Flow Around Bluff-Bodies
Arrangement
El˙zbieta Mory´n-Kucharczyk and Renata Gnatowska 49
9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
9.2 Results ofMeasurements 50
9.3 Conclusions 52
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
10 On the Atmospheric Flow Modelling over Complex Relief
Ivo Sl´adek, Karel Kozel and Zbyˇnek Jaˇnour 55
10.1 Mathematical Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
10.1.1 Turbulence Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
10.1.2 Boundary Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
10.1.3 Numerical Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
10.2 Definition of the Computational Case . . . . . . . . . . . . . . . . . . . . . . . . 57
10.2.1 Some Numerical Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
10.3 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
11 Comparison of Logarithmic Wind Profiles and Power
Law Wind Profiles and their Applicability for Offshore
Wind Profiles
Stefan Emeis and Matthias T¨urk 61
11.1 Wind Profile Laws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
11.2 Comparison of Profile Laws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
11.3 Application to Offshore Wind Profiles . . . . . . . . . . . . . . . . . . . . . . . . 62
11.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
12 Turbulence Modelling and Numerical Flow Simulation
of Turbulent Flows
Claus Wagner 65
12.1 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

12.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
12.3 Governing Equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
12.4 Direct Numerical Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
12.5 Statistical Turbulence Modelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
X Contents
12.6 Subgrid Scale Turbulence Modelling . . . . . . . . . . . . . . . . . . . . . . . . . 68
12.6.1 Eddy Viscosity Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
12.6.2 Scale Similarity Modelling . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
12.7 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
13 Gusts in Intermittent Wind Turbulence
and the Dynamics of their Recurrent Times
Fran¸cois G. Schmitt 73
13.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
13.2 Scaling and Intermittency of Velocity Fluctuations . . . . . . . . . . . . . 74
13.3 Gusts for Fixed Time Increments
and Their Recurrent Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
13.4 The Dynamics of Inverse Times: Times Needed
for Fluctuations Larger than a Fixed Velocity Threshold . . . . . . . 78
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
14 Report on the Research Project OWID – Offshore Wind
Design Parameter
T. Neumann, S. Emeis and C. Illig 81
14.1 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
14.2 Relevant Standards and Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . 81
14.3 Normal Wind Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
14.4 Normal Turbulence Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
14.5 Extreme Wind Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
14.6 Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
14.7 Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
15 Simulation of Turbulence, Gusts and Wakes for Load
Calculations
Jakob Mann 87
15.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
15.2 Simulation over Flat Terrain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
15.3 Constrained Gaussian Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
15.4 Wakes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
15.4.1 Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
15.4.2 Scanning Laser Doppler Wake Measurements . . . . . . . . . . 90
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
16 Short Time Prediction of Wind Speeds
from Local Measurements
Holger Kantz, Detlef Holstein, Mario Ragwitz and Nikolay K. Vitanov . 93
16.1 Wind Speed Predictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
16.2 Prediction of Wind Gusts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
Contents XI
17 Wind Extremes and Scales: Multifractal Insights
and Empirical Evidence
I. Tchiguirinskaia, D. Schertzer, S. Lovejoy and J.M. Veysseire 99
17.1 Atmospheric Dynamics, Cascades and Statistics . . . . . . . . . . . . . . . 99
17.2 Extremes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
17.3 Discussion and Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
18 Boundary-Layer Influence on Extreme Events in Stratified
Flows over Orography
Karine Leroux and Olivier Eiff 105
18.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
18.2 Experimental Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

18.3 Basic Flow Pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
18.4 Downstream Slip Condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
18.5 Boundary Layer and Wave Field Interaction . . . . . . . . . . . . . . . . . . 108
18.6 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
19 The Statistical Distribution of Turbulence Driven
Velocity Extremes in the Atmospheric Boundary Layer –
Cartwright/Longuet-Higgins Revised
G.C. Larsen and K.S. Hansen 111
19.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
19.2 Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
20 Superposition Model for Atmospheric Turbulence
S. Barth, F. B¨ottcher and J. Peinke 115
20.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
20.2 Superposition Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
20.3 Conclusions and Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
21 Extreme Events Under Low-Frequency Wind Speed
Variability and Wind Energy Generation
Alin A. Cˆarsteanu and Jorge J. Castro 119
21.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
21.2 Mathematical Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
21.3 Results and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
21.4 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
XII Contents
22 Stochastic Small-Scale Modelling of Turbulent Wind
Time Series
Jochen Cleve and Martin Greiner 123

22.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
22.2 Consistent Modelling of Velocity and Dissipation . . . . . . . . . . . . . . 123
22.3 Refined Modelling: Stationarity and Skewness . . . . . . . . . . . . . . . . . 124
22.4 Statistics of the Artificial Velocity Signal . . . . . . . . . . . . . . . . . . . . . 126
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
23 Quantitative Estimation of Drift and Diffusion Functions
from Time Series Data
David Kleinhans and Rudolf Friedrich 129
23.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
23.2 Direct Estimation of Drift and Diffusion . . . . . . . . . . . . . . . . . . . . . . 130
23.3 Stability of the Limiting Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . 131
23.4 Finite Length of Time Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
23.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
24 Scaling Turbulent Atmospheric Stratification:
A Turbulence/Wave Wind Model
S. Lovejoy and D. Schertzer 135
24.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
24.2 An Extreme Unlocalized (Wave) Extension . . . . . . . . . . . . . . . . . . . 136
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
25 Wind Farm Power Fluctuations
P. Sørensen, J. Mann, U.S. Paulsen and A. Vesth 139
25.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
25.2 Test Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
25.3 PSDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
25.4 Coherence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
25.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
26 Network Perspective of Wind-Power Production
Sebastian Jost, Mirko Sch¨afer and Martin Greiner 147

26.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
26.2 Robustness in a Critical-Infrastructure Network Model . . . . . . . . . 147
26.3 Two Wind-Power Related Model Extensions . . . . . . . . . . . . . . . . . . 151
26.4 Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
Contents XIII
27 Phenomenological Response Theory to Predict
Power Output
Alexander Rauh, Edgar Anahua, Stephan Barth and Joachim Peinke 153
27.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
27.2 Power Curve from Measurement Data . . . . . . . . . . . . . . . . . . . . . . . . 154
27.3 Relaxation Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
27.4 Discussion and Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158
28 Turbulence Correction for Power Curves
K. Kaiser, W. Langreder, H. Hohlen and J. Højstrup 159
28.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
28.2 Turbulence and Its Impact on Power Curves . . . . . . . . . . . . . . . . . . 160
28.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
28.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
29 Online Modeling of Wind Farm Power
for Performance Surveillance and Optimization
J.J. Trujillo, A. Wessel, I. Waldl and B. Lange 163
29.1 Wind Turbine Power Modeling Approach . . . . . . . . . . . . . . . . . . . . . 163
29.1.1 Wind Farm Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
29.1.2 Online Wind Farm Model . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
29.2 Measurements and Simulation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
29.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

30 Uncertainty of Wind Energy Estimation
T. Weidinger,
´
A. Kiss, A.Z. Gy¨ongy¨osi, K. Krassov´an and B. Papp 167
30.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
30.2 Wind Climate of Hungary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
30.3 The Uncertainty of the Power Law Wind Profile Estimation . . . . 169
30.4 Inter-Annual Variability of Wind Energy . . . . . . . . . . . . . . . . . . . . . 169
30.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
31 Characterisation of the Power Curve for Wind Turbines
by Stochastic Modelling
E. Anahua, S. Barth and J. Peinke 173
31.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
31.2 Simple Relaxation Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
31.3 Langevin Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
31.4 Data Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
31.5 Conclusion and Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
XIV Contents
32 Handling Systems Driven by Different Noise Sources:
Implications for Power Curve Estimations
F. B¨ottcher, J. Peinke, D. Kleinhans and R. Friedrich 179
32.1 Power Curve Estimation in a Turbulent Environment . . . . . . . . . . 179
32.1.1 Reconstruction of a Synthetic Power Curve . . . . . . . . . . . . 180
32.1.2 Additional Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
32.2 Conclusions and Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
33 Experimental Researches of Characteristics of Windrotor
Models with Vertical Axis of Rotation

Stanislav Dovgy, Vladymyr Kayan and Victor Kochin 183
33.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
33.2 Experimental Installation and Models . . . . . . . . . . . . . . . . . . . . . . . . 184
33.3 Performance Characteristics of Windrotor Models . . . . . . . . . . . . . 184
33.4 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
34 Methodical Failure Detection in Grid Connected
Wind Parks
Detlef Schulz, Kaspar Knorr and Rolf Hanitsch 187
34.1 Problem Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
34.2 Doubly-fed Induction Generators . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
34.3 Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
34.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
35 Modelling of the Transition Locations
on a 30% thick Airfoil with Surface Roughness
Benjamin Hillmer, Yun Sun Chol and Alois Peter Schaffarczyk 191
35.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
35.2 Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
35.3 Modelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
35.4 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
35.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
36 Helicopter Aerodynamics with Emphasis Placed
on Dynamic Stall
Wolfgang Geissler, Markus Raffel, Guido Dietz and Holger Mai 199
36.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
36.2 The Phenomenon Dynamic Stall . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
36.3 Numerical and Experimental Results
forthe TypicalHelicopter AirfoilOA209 201
36.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
Contents XV
37 Determination of Angle of Attack (AOA) for Rotating
Blades
Wen Zhong Shen, Martin O.L. Hansen and Jens Nørkær Sørensen 205
37.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
37.2 Determination of Angle of Attack . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
37.3 Numerical Results and Comparisons . . . . . . . . . . . . . . . . . . . . . . . . . 207
37.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
38 Unsteady Characteristics of Flow Around an Airfoil
at High Angles of Attack and Low Reynolds Numbers
Hui Guo, Hongxing Yang, Yu Zhou and David Wood 211
38.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
38.2 Test Facility and Setup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
38.3 Experimental Results and Discussions . . . . . . . . . . . . . . . . . . . . . . . . 212
38.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
39 Aerodynamic Multi-Criteria Shape Optimization
of VAWT Blade Profile by Viscous Approach
R´emi Bourguet, Guillaume Martinat, Gilles Harran
and Marianna Braza 215
39.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
39.2 Physical Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
39.2.1 Templin Method for Efficiency Graphe Computation . . . . 215
39.2.2 Flow Simulation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
39.3 Blade Profile Optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
39.3.1 Optimization Method: DOE/RSM . . . . . . . . . . . . . . . . . . . . 216
39.3.2 Reaching the Global Optimum . . . . . . . . . . . . . . . . . . . . . . . 217
39.4 Numerical Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217

39.4.1 Validation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217
39.4.2 Optimization Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217
39.5 Conclusion and Prospects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
40 Rotation and Turbulence Effects on a HAWT Blade
Airfoil Aerodynamics
Christophe Sicot, Philippe Devinant, Stephane Loyer
and Jacques Hureau 221
40.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
40.2 Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
40.3 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
40.3.1 Mean Pressure Values Analysis . . . . . . . . . . . . . . . . . . . . . . . 222
40.3.2 Instantaneous Pressure Distributions Analysis. . . . . . . . . . 224
40.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
XVI Contents
41 3D Numerical Simulation and Evaluation of the Air Flow
Through Wind Turbine Rotors with Focus on the Hub Area
J. Rauch, T. Kr¨amer, B. Heinzelmann, J. Twele and P.U. Thamsen 227
41.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227
41.2 Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228
41.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228
41.4 Perspective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
42 Performance of the Risø-B1 Airfoil Family for Wind
Turbines
Christian Bak, Mac Gaunaa and Ioannis Antoniou 231
42.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231
42.2 The Wind Tunnel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231
42.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232

42.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
42.5 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234
43 Aerodynamic Behaviour of a New Type of Slow-Running
VAW T
J L. Menet 235
43.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235
43.2 Description of the Savonius Rotors . . . . . . . . . . . . . . . . . . . . . . . . . . 236
43.3 Description of the Numerical Model. . . . . . . . . . . . . . . . . . . . . . . . . . 236
43.4 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237
43.4.1 Optimised Savonius Rotor . . . . . . . . . . . . . . . . . . . . . . . . . . . 237
43.4.2 The New Rotor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238
43.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239
44 Numerical Simulation of Dynamic Stall using Spectral/hp
Method
B. Stoevesandt, J. Peinke, A. Shishkin and C. Wagner 241
44.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241
44.2 The Spectral/hp Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
44.3 The NekTar Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243
44.4 First Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244
44.5 Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244
45 Modeling of the Far Wake behind a Wind Turbine
Jens N. Sørensen and Valery L. Okulov 245
45.1 Extended Joukowski Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
45.2 Unsteady Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247
Contents XVII
45.3 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248

46 Stability of the Tip Vortices in the Far Wake
behind a Wind Turbine
Valery L. Okulov and Jens N. Sørensen 249
46.1 Theory: Analysis of the Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249
46.2 Application of the Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251
46.3 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
47 Modelling Turbulence Intensities Inside Wind Farms
Arne Wessel, Joachim Peinke and Bernhard Lange 253
47.1 Description of the Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
47.1.1 Single Wake Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
47.1.2 Superposition of the Wakes . . . . . . . . . . . . . . . . . . . . . . . . . . 254
47.2 Comparison of the Model with Wake Measurements. . . . . . . . . . . . 254
47.2.1 Vindeby Double and Quintuple Wake . . . . . . . . . . . . . . . . . 254
47.3 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256
48 Numerical Computations of Wind Turbine Wakes
Stefan Ivanell, Jens N. Sørensen and Dan Henningson 259
48.1 Numerical Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
48.2 Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
49 Modelling Wind Turbine Wakes with a Porosity Concept
Sandrine Aubrun 265
49.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265
49.2 Experimental Set-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265
49.3 Results for Homogeneous Freestream Conditions . . . . . . . . . . . . . . 266
49.4 Results for Shear Freestream Conditions . . . . . . . . . . . . . . . . . . . . . . 267
49.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269
50 Prediction of Wind Turbine Noise Generation

and Propagation based on an Acoustic Analogy
Drago¸s Moroianu and Laszlo Fuchs 271
50.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271
50.2 Problem Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271
50.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272
50.3.1 Flow Computations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272
50.3.2 Acoustic Computations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273
50.3.3 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274
XVIII Contents
51 Comparing WAsP and Fluent for Highly Complex Terrain
Wind Prediction
D. Cabez´on, A. Iniesta, E. Ferrer and I. Mart´ı 275
51.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275
51.2 Alaiz Test Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275
51.3 Description of the Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276
51.3.1 Linear Models. WAsP 8.1 (Wind Atlas Analysis
and Application Program) and WAsP Engineering 2.0 . . 276
51.3.2 Non Linear Models. Fluent 6.2 . . . . . . . . . . . . . . . . . . . . . . . 276
51.4 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276
51.4.1 Wind Speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276
51.4.2 Turbulence Intensity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279
51.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279
52 Fatigue Assessment of Truss Joints Based on Local
Approaches
H. Th. Beier, J. Lange and M. Vormwald 281
52.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281
52.2 Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281
52.2.1 Fatigue Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 282

52.2.2 Crack Initiation with Local Strain Approach . . . . . . . . . . . 282
52.2.3 Crack Growth with Linear Elastic Fracture Mechanics . . 283
52.2.4 Fracture Criterion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284
52.2.5 Endurance Limit with Local Stress Approach . . . . . . . . . . 284
52.3 Examples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284
52.3.1 Truss-joint with Pre-cut Gusset Plates (PCGP-joint) . . . 284
52.3.2 Stiffener of the Great Wind Energy
ConverterGROWIAN 284
52.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286
53 Advances in Offshore Wind Technology
Marc Seidel and Jens G¨oßwein 287
53.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287
53.2 Wind Turbine Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287
53.3 Substructure Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
53.3.1 Design Methodologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
53.3.2 Substructure Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290
53.4 Installation Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291
Contents XIX
54 Benefits of Fatigue Assessment with Local Concepts
P. Schaumann and F. Wilke 293
54.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
54.2 Applied Local Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
54.3 Comparison of Fatigue Design for a Tripod . . . . . . . . . . . . . . . . . . . 294
54.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
55 Extension of Life Time of Welded Fatigue Loaded
Structures
Thomas Ummenhofer, Imke Weich and Thomas Nitschke-Pagel 297

55.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297
55.2 Background. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297
55.2.1 Weld Improvement Methods . . . . . . . . . . . . . . . . . . . . . . . . . 297
55.3 Experimental Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298
55.3.1 Testing Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298
55.4 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298
55.4.1 Initial State of the Fatigue Test Samples . . . . . . . . . . . . . . 298
55.4.2 Results of the Fatigue Tests . . . . . . . . . . . . . . . . . . . . . . . . . 299
55.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300
56 Damage Detection on Structures of Offshore Wind
Turbines using Multiparameter Eigenvalues
Johannes Reetz 301
56.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301
56.2 The Multiparameter Eigenvalue Method . . . . . . . . . . . . . . . . . . . . . . 301
56.3 Validation of the Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303
56.4 Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304
57 Influence of the Type and Size of Wind Turbines
on Anti-Icing Thermal Power Requirements for Blades
L. Battisti, R. Fedrizzi, S. Dal Savio and A. Giovannelli 305
57.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305
57.2 Analysis of the Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306
57.3 Anti-Icing Power as a Function of the Machine Size . . . . . . . . . . . . 306
57.4 Anti-Icing Power as a Function of the Machine Type . . . . . . . . . . . 307
57.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308
58 High-cycle Fatigue of “Ultra-High Performance Concrete”
and “Grouted Joints” for Offshore Wind Energy Turbines
L. Lohaus and S. Anders 309

58.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
58.2 Ultra-High Performance Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
XX Contents
58.3 Ultra-High Performance Concrete in Grouted Joints . . . . . . . . . . . 310
58.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312
59 A Modular Concept for Integrated Modeling of Offshore
WEC Applied to Wave-Structure Coupling
Kim Mittendorf, Martin Kohlmeier, Abderrahmane Habbar and
Werner Zielke 313
59.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313
59.2 Integrated Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313
59.2.1 Model Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315
59.2.2 Model Realization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315
59.3 Modeling of Wave Loads on the Support Structure Offshore
WindEnergyTurbines 316
59.3.1 Application to the Support Structure of an Offshore
WindTurbine 316
59.4 Future Demands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317
60 Solutions of Details Regarding Fatigue
and the Use of High-Strength Steels for Towers of Offshore
Wind Energy Converters
J. Bergers, H. Huhn and R. Puthli 319
60.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319
60.2 Fatigue Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
60.3 Finite-Element Analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324
61 On the Influence of Low-Level Jets on Energy Production
and Loading of Wind Turbines

N. Cosack, S. Emeis and M. K¨uhn 325
61.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
61.2 Data and Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
61.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326
61.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328
62 Reliability of Wind Turbines
Berthold Hahn, Michael Durstewitz and Kurt Rohrig 329
62.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329
62.2 Data Basis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329
62.3 Break Down of Wind Turbines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330
62.4 Malfunctions of Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331
62.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332
List of Contributors
Edgar Anahua
ForWind – Center for
Wind Energy Research
University of Oldenburg
D-26111 Oldenburg
Germany

S. Anders
Institute of Building Materials
University of Hannover
Appelstraße 9A, 30161 Hannover
Germany
Ioannis Antoniou
Department of Wind Energy
Risø National Laboratory

P.O. Box 49
DK-4000 Roskilde
Denmark
Sandrine Aubrun
Laboratoire de M´ecanique et
d’Energ´etique, 8 rue L´eonard de
Vinci, F-45072 Orl´eans cedex
France

Christian Bak
Department of Wind Energy
Risø National Laboratory
P.O. Box 49
DK-4000 Roskilde
Denmark

Stephan Barth
ForWind – Center for
Wind Energy Research
University of Oldenburg
D-26111 Oldenburg
Germany

L. Battisti
DIMS – University of Trento
via Mesiano 77, 38050, Trento
Italy
H. Th. Beier
IFSW, Technische Universit¨at
Darmstadt, Petersenstr. 12

64287 Darmstadt
Germany
J. Bergers
Research Centre for Steel
Timber and Masonry
University of Karlsruhe
Germany
XXII List of Contributors
Lars Bergdahl
Water Environment Technology
Chalmers, 412 96 G¨oteborg, Sweden

Etienne Bibor
Department of Mechanical
Engineering, Ecole de technologie
superieure, 1100 Notre-Dame Ouest
Montreal, Canada

Wim Bierbooms
Delft University of Technology
2629 HS Delft, The Netherlands
R´emi Bourguet
Institut de M´ecanique des Fluides
de Toulouse, 6 all´ee du
Professeur Camille Soula, Toulouse
France

F. B¨ottcher
ForWind – Center for Wind Energy
Research, University of Oldenburg

D-26111 Oldenburg, Germany
Marianna Braza
Institut de M´ecanique des
Fluides de Toulouse, 6 all´ee du
Professeur Camille Soula, Toulouse
France
J.A.T. Bye
The University of Melbourne
Victoria 3010, Australia
D. Cabez´on
Department of Wind Energy
National Renewable
Energy Centre (CENER)
C/Ciudad de la Innovacin
31621 Sarriguren, Navarra
Spain
Alin A. Cˆarsteanu
Department of Mathematics
Cinvestav, Av. IPN 2508, Mexico
D.F. 07360, Mexico
F.A. Castro
CEsA – Research Centre for Wind
Energy and Atmospheric Flows
Faculdade de Engenharia da
Universidade do Porto Rua Roberto
Frias s/n, 4200-465 Porto
Portugal
Jorge J. Castro
Department of Physics, Cinvestav
Av. IPN 2508, Mexico D.F. 07360

Mexico
Yun Sun Chol
Department of Mathematics
and Mechanics, Kim Il Sung
University, Pyongyang
DPR of Korea
Jochen Cleve
Institute of Theoretical Physics
TU Dresden, D-01062 Dresden
Germany

N. Cosack
Endowed Chair of Wind Energy
Institute of Aircraft Design
University of Stuttgart
Allmandring 5b, 70550 Stuttgart
Germany
S. Dal Savio
DIMS – University of Trento
via Mesiano 77, 38050, Trento
Italy
Philippe Devinant
Laboratoire de M´ecanique
et Energ´etique
Universit´ed’Orl´eans
8rueL´eonard de Vinci
45072 Orl´eans, France
List of Contributors XXIII
Guido Dietz
DLR-G¨ottingen, Bunsenstr. 10

37073 G¨ottingen, Germany
Stanislav Dovgy
Institute of Hydromechanics NASU
Kyiv, Ukraine
Michael Durstewitz
Institut f¨ur Solare
Energieversorgungstechnik (ISET)
Verein an der Universit¨at
Kassel e.V., 34119 Kassel
Germany
Fritz Eb ert
Institute for Mechanical Process
Engineering
University of Kaiserslautern
Erwin-Schr¨odinger-Strasse 44
67663 Kaiserslautern, Germany

Olivier Eiff
Institut de M´ecanique des Fluides
de Toulouse, all´ee du
Professeur Camille Soula
31400 Toulouse, France

Stefan Emeis
Institut f¨ur Meteorologie und
Klimaforschung, Forschungszentrum
Karlsruhe Kreuzeckbahnstr. 19
Garmisch-Partenkirchen, Germany

Claes Eskilsson

Water Environment Technology
Chalmers, 412 96 G¨oteborg, Sweden

Manfred Fallen
Institute for Fluid Machinery
and Fluid Mechanics
University of Kaiserslautern
Erwin-Schr¨odinger-Strasse 44
67663 Kaiserslautern
Germany

R. Fedrizzi
DIMS – University of Trento
viaMesiano77
38050 Trento, Italy
E. Ferrer
Department of Wind Energy
National Renewable Energy Centre
(CENER)
C/Ciudad de la Innovacin
31621 Sarriguren, Navarra, Spain
Rudolf Friedrich
Westf¨alische Wilhelms-Universit¨at
M¨unster
Institut f¨ur Theoretische Physik
48149 M¨unster
Germany
Laszlo Fuchs
Lund University,
Division of Fluid Mechanics

Ole R¨omersv. 1
P.O. Box 118
22100 Lund
Sweden

Wolfgang Geissler
DLR-G¨ottingen, Bunsenstr. 10
37073 G¨ottingen
Germany
A. Giovannelli
University of Rome3, via della Vasca
Navale 79, 00146, Rome
XXIV List of Contributors
Renata Gnatowska
Institute of Thermal Machinery
Czestochowa University
of Technology
Poland

Jens G¨oßwein
REpower Systems AG, Hollesenstr.
15, 24768 Rendsburg, Germany
Martin Greiner
Corporate Technology
Information and Communications
Siemens AG, D-81730 M¨unchen
Germany

S.E. Gryning
Department of Wind Energy

Risø, DK-4000, Roskilde
Denmark
Hui Guo
Department of Building Services
Engineering
The Hong Kong Polytechnic
University
Hong Kong, China
and
School of Aeronautical Science
and Engineering
Beijing University of Aeronautics
and Astronautics
Beijing, China
A.Z. Gy¨ongy¨osi
Department of Meteorology,
E¨otv¨os University, P´azm´any St. 1/A
Budapest, Hungary
Abderrahmane Habbar
ForWind – Center for Wind Energy
Research
Institute of Fluid Mechanics
and Computer Applications in Civil
Engineering University of Hannover
Appelstr. 9A, 30167 Hannover
Germany
Berthold Hahn
Institut f¨ur Solare Energiever-
Sorgungstechnik (ISET)
Verein an der Universit¨at Kassel

e.V., 34119 Kassel, Germany
Rolf Hanitsch
Technical University Berlin
Einsteinufer 11
Berlin
Germany

K.S. Hansen
Technical University of Denmark
DK-2800 Lyngby, Denmark
Martin O.L. Hansen
Department of Mechanical
Engineering
Technical University of Denmark
Building 403
2800 Lyngby
Denmark

Gilles Harran
Institut de M´ecanique des Fluides
de Toulouse, 6 all´ee du
Professeur Camille Soula, Toulouse
France
B. Heinzelmann
Fluidsystemdynamik
Technische Universit¨at Berlin
Sekr. K2, Straße des 17. Juni 135
10623 Berlin, Germany

Dan Henningson

Royal Institute of Technology
Stockholm, Sweden

List of Contributors XXV
Benjamin Hillmer
Computational Mechanics
Laboratory
University of Applied Sciences
Kiel, Grenzstr. 3
24149 Kiel
Germany

H. Hohlen
EU Energy Wind Turbines
Seelandstr. 1
23569 L¨ubeck
Germany
J. Højstrup
Suzlon Energy A/S, Kystvejen 29
8000
˚
Arhus, Denmark
Detlef Holstein
Max Planck Institute for
the Physics of Complex Systems
N¨othnitzer Str. 38, 01187 Dresden
Germany
H. Huhn
IMS Ingenieurgesellschaft mbH
Hamburg, Germany

Jacques Hureau
Laboratoire de M´ecanique
et Energ´etique,
Universit´ed’Orl´eans
8rueL´eonard de Vinci
45072 Orl´eans, France
C. Illig
DEWI-OCC Offshore and
Certification Centre GmbH
Am Seedeich 9, Cuxhaven
Germany
A. Iniesta
Department of Wind Energy
National Renewable Energy Centre
(CENER)
C/Ciudad de la Innovacin, 31621
Sarriguren, Navarra, Spain
Stefan Ivanell
Royal Institute of Technology
Stockholm, Sweden
Gotland University, Visby
Sweden

Zbyˇnek Jaˇnour
Institute of Thermomechanics
Czech Academy of Sciences
Dolejˇskova 5, ZIP 182 00, Prague
Czech Republic

N.O. Jensen

Department of Wind Energy
Risø DK-4000, Roskilde
Denmark
H.E. Jørgensen
Department of Wind Energy, Risø
DK-4000, Roskilde, Denmark
Sebastian Jost
Corporate Technology
Information and Communications
Siemens AG
D-81730 M¨unchen, Germany

K. Kaiser
Ingenieurb¨uro, Gr. Burgstr. 27
23552 L¨ubeck, Germany
Holger Kantz
Max Planck Institute for the Physics
of Complex Systems,
N¨othnitzer Str. 38, 01187 Dresden
Germany

Vladymyr Kayan
Institute of Hydromechanics NASU
Kyiv, Ukraine

XXVI List of Contributors
A. Kiss
Department of Atomic Physics
E¨otv¨os University, P´azm´any
St. 1/A, Budapest, Hungary

David Kleinhans
Westf¨alische Wilhelms-Universit¨at
M¨unster, Institut f¨ur Theoretische
Physik
48149 M¨unster
Germany
Kaspar Knorr
Technical University Berlin
Einsteinufer 11, Berlin, Germany
Victor Kochin
Institute of Hydromechanics NASU
Kyiv, Ukraine
Martin Kohlmeier
ForWind – Center for Wind Energy
Research
Institute of Fluid Mechanics and
Computer Applications in Civil
Engineering University of Hannover
Appelstr. 9A, 30167 Hannover
Germany
Karel Kozel
Czech Technical University
in Prague, U12101, Karlovo
n´amˇest´ı 13, ZIP 121 35
Czech Republic

T. Kr¨amer
Fluidsystemdynamik, Technische
Universit¨at Berlin, Sekr. K2
Straße des 17. Juni 135

10623 Berlin, Germany
K. Krassov´an
Department of Atomic Physics
E¨otv¨os University, P´azm´any St.
1/A, Budapest, Hungary
M. K¨uhn
Endowed Chair of Wind Energy
Institute of Aircraft Design
University of Stuttgart
Allmandring 5b, 70550 Stuttgart
Germany
Bernhard Lange
ISET e.V., K¨onigstor 59
34119 Kassel, Germany

J. Lange
IFSW, Technische Universit¨at
Darmstadt, Petersenstr. 12
64287 Darmstadt, Germany
W. Langreder
Wind Solutions,
Engelsgrube 25 23552 L¨ubeck
Germany
G.C. Larsen
Department of Wind Energy
Risø National Laboratories
DK-4000 Roskilde, Denmark
S.E. Larsen
Department of Wind Energy, Risø
DK-4000, Roskilde, Denmark

Karine Leroux
Centre National de Recherches
M´et´eorologiques de Toulouse
M´et´eo-France, 42 av. G. Coriolis
31057 Toulouse Cedex, France
and
Institut de M´ecanique des Fluides
de Toulouse, all´ee du
Professeur Camille Soula
31400 Toulouse, France